Camera to flash adapter

ABSTRACT

A system and method for adapting a multi-purpose electronic flash for use with an automatic exposure control camera is disclosed. The system responds to a ready signal from the multi-purpose flash and a reference signal from the automatic exposure control camera by providing a signal representative of the correct aperture for a given film speed (ASA) and range of flash to subject distances. Film speed is provided to the system by setting one portion of a variable resistance, while range is provided to the system by setting another portion of the variable resistance which is associated with a graded density optical filter located in front of the photosensor. A bipolar range about the reference signal is established to permit positive or negative signal excursions about the reference signal for indication of correct aperture. A scaling amplifier may also be provided for signal conditioning to ensure compatibility with the camera. The scaling amplifier may be arranged to provide less than unity amplification, thereby reducing system error. A special housing connects between the foot of the flash and the camera to provide access to the camera accessory shoe terminals and also to permit the flash to be operated on or off the camera. Various alternatives are disclosed.

This is a continuation of application Ser. No. 306,245 filed Sept. 28,1981, now U.S. Pat. No. 4,474,450, and also is a division of applicationSer. No. 537,251 filed Sept. 28, 1983, now abandoned, both of which area continuation of application Ser. No. 019,297 filed Mar. 12, 1979, nowabandoned.

FIELD OF THE INVENTION

The present invention relates generally to automatic flash devices, andmore particularly to automatic flash devices for use with automaticexposure control cameras.

BACKGROUND OF THE INVENTION

Automatic flash equipment has been developed wherein the amount of lightsupplied by the flash is determined by range, which is a combination ofthe reflectivity of the scene together with flash to subject distance,camera aperture, and film speed. In such equipment the flash tube isturned off, or quenched, when sufficient light has been reflected fromthe scene for the selected aperture and film speed. One such automaticflash is disclosed in U.S. Pat. No. 3,809,951.

More recently, similar automatic flashes have been developed for usewith automatic exposure cameras such as the Canon AE-1, the Olympus OM-2and others. Examples of such systems are disclosed in U.S. Pat. Nos.4,047,194; 4,079,385; 4,078,242; and 4,095,242. Such flash systems areusually dedicated for use with the particular camera, and operate inconjunction with the exposure control system of the automatic exposurecamera, and more usually a shutter-preferred automatic exposure camera,to determine the amount of light to be supplied by the flash. Ingeneral, the dedicated flash provides a signal to the camera whichcauses the camera to automatically pre-set the aperture, and the flash,when fired, supplies only the amount of light appropriate for thataperture. Also, the dedicated flash provides a ready signal which causesthe camera to set the shutter to a flash synchronization speed. However,it has thus far not been possible to operate the dedicated flashremotely from the camera in conjunction with the exposure control systemof the camera, while sensing the amount of reflected light received atthe camera.

Thus far, however, it has not been possible to use a conventionalautomatic flash in conjunction with the automatic exposure feature ofsuch cameras. Thus the purchase of such an automatic exposure camera hasrequired the purchase of an associated, dedicated flash, or the use ofthe automatic exposure camera in a manual mode with a conventionalautomatic flash. There has therefore been a need for a means by whichconventional automatic flash could be adapted for use in conjunctionwith the exposure control system of an automatic exposure camera, andwhich would permit off camera operation while still sensing the amountof reflected light received at the camera.

SUMMARY OF THE INVENTION

The present invention provides a means and apparatus by which aconventional automatic flash may be adapted for use with the exposurecontrol systems of automatic exposure cameras.

The adapter of the present invention utilizes signals available from theautomatic exposure camera together with those from a non-dedicated ormulti-purpose flash to cause the camera to set the shutter to a flashsynchronization speed. The adapter also causes the aperture of theautomatic exposure camera to be set in accordance with the inputs to theflash for film speed and range. Turn-off circuitry of the flash thenquenches the flash tube when the amount of light appropriate for theselected aperture has been emitted.

The adapter causes the camera to set the shutter to a flashsynchronization speed in response to a ready signal from the flashitself. The ready signal permits a buffer amplifier of the adapter todraw current from the reference terminal of the camera, thereby causingthe camera to set the shutter to a speed synchronized for flashphotography.

In addition, film speed and range are optically and electrically encodedinto the adapter by means of a variable resistance associated with agraded density optical filter, in combination with other circuitry.Unlike prior art dedicated flashes, the adapter of the present inventionmay be arranged to provide a continuum of ranges as well as providing amore efficient method for encoding such information.

The encoded film speed and range are translated by the adapter into anaperture setting signal by means of a multiplying amplifier and ascaling amplifier. The multiplying amplifier provides a signal which isamplified with respect to the reference signal provided by the camera.The output of the multiplying amplifier is then divided through thevariable resistance to provide a signal representative of theappropriate aperture for the film speed and range settings.

The aperture signal is then scaled for use with the particular camera bymeans of a scaling amplifier. For the embodiment described herein, thegain of the scaling amplifier stage is less than unity, therebyproportionately reducing any error resulting in earlier stages of theadapter circuitry. The scaling amplifier also subtracts the camerareference voltage, resulting in an aperture setting signal which isbipolar about the camera reference signal and compatible therewith. Thissignal is then supplied to the camera and causes the correct aperture tobe selected for the particular conditions.

Additionally, the adapter of the present invention includes a housingwhich mounts between the flash and the camera accessory shoe and locksthe flash and adapter onto the camera. The housing provides accessbetween the terminals located on the camera accessory shoe and thecircuitry of the adapter. Also, the multi-purpose flash may be cableconnected to the adapter to permit the flash to be remotely located eventhough the adapter remains attached to the camera. This permits remoteflash positioning while still sensing the amount of light reflected onthe camera.

It is therefore one object of the present invention to provide anapparatus suitable for permitting a nondedicated flash to be used withthe automatic exposure circuitry of a camera.

It is another object of the present invention to provide a new method ofencoding information.

It is yet another object of the present invention to provide a novelmethod of providing film speed and range information to camera automaticexposure circuitry.

These and other objects of the present invention can be betterappreciated from the following detailed description together with theappended drawings, in which

FIG. 1 illustrates in exploded view the relationship of themulti-purpose flash, the adapter of the present invention including itshousing, and the accessory shoe of an automatic exposure camera;

FIG. 2 is a schematic diagram of the circuitry of one embodiment of thepresent invention;

FIG. 3 is a cross-sectional side view of the sensor mechanism of theembodiment shown in FIG. 2;

FIG. 4a is a side view of the adapter of the present invention mountedbetween the camera and the flash;

FIGS. 4b and 4d are cut-away side view of FIG. 4a showing the lockingfeature of the adapter of the present invention; and

FIG. 4c is a detail plan view of the interior of the adapter baseshowing the locking feature of the present invention.

FIG. 5 is a block diagram of a conventional prior art multi-purposeflash.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIG. 1, the relationship between the adapter of thepresent invention 1, a multi-purpose flash 2 and the accessory shoe 3 ofan automatic exposure camera is shown. One suitable flash is the VivitarModel 285, and a suitable automatic exposure camera is the Canon AE-1,although many similar devices are suitable for use with the presentinvention. As can be seen from FIG. 1, the foot 4 of the flash 2 fitsinto a shoe 5 of a housing 9 of the adapter 1, and the adapter 1 couplesto the accessory shoe 3 by means of a base, all of which are describedin greater detail in connection with FIGS. 4a-4c. Additionally, thesensor portion 7 of the adapter 1 couples to a socket 8 of the flash 2where a removable sensor is normally located, as described in greaterdetail hereinafter.

Turning first to FIG. 5, the same illustrates a conventional prior artautomatic electronic flash unit, such as the Model 285 noted above, inblock diagram form. The flash unit includes a main capacitor A, flashtube B, flash initiating or discharge means C and H, flash terminatingor quench means D, light sensor circuit D1, source of electrical powerE, and a light sensor F. Also shown is a camera "sync" input to the footor hot shoe 4 of the flash unit 2. Additionally, FIG. 5 shows the socket8 of the flash 2 for accommodating the removable light sensor F (and forreceiving a connector of the adapter of the present invention to bedescribed below).

The flash initiating means typically includes a series switch C andtrigger transformer circuit H. When a sync signal is received from anassociated camera, the series switch C is turned "on" and the triggertransformer circuit H triggers the flash tube B by ionizing the gastherein. This causes the resistance of the flash tube to decrease to alow value, and the charge on the main capacitor A is dumped into theflash tube B, causing it to emit light. The light sensor F senses lightreflected from the subject being photographed, and when sufficient lighthas been received as determined by the light sensor circuit D1, theterminating means D operates to quench the flash of light, typically bycommutating the series switch C, in a conventional manner.

Referring now to FIG. 2, which illustrates in schematic diagram form thecircuitry of one embodiment of the present invention, it can be seenthat the adapter 1 couples to the flash 2 by means of a connector 10which includes a plurality of pins 12, 14, 16 and 18 (also shown in FIG.1). Also, the adapter 1 couples to the terminals of the accessory shoe 3by means of a connector 20 having thereon electrical terminals 22, 24,26 and 28 arranged to match the corresponding terminals on the accessoryshoe 3 of the camera. A flash trigger signal is supplied at the terminal22, while a camera reference signal is supplied at the terminal 24. Theadapter 1 supplies an aperture setting signal to the camera via theterminal 26 as described in detail hereinafter. The terminal 28 connectsthe ground or common signal on the adapter to that signal on the camera.

When the flash 2 is connected via the adapter 1 to the camera and theflash is sufficiently charged to be tiggerable, a ready signal developson the pin 12, which is also tied to the trigger terminal 22. The readysignal may be developed by monitoring the anode voltage of theelectronic flash, or may be supplied by a detector, such as acomparator, internal to the flash, for example the detector containedwithin the Vivitar Model 285 flash. If the flash ready signal is notsupplied by a detector internal to the flash, the terminals 12 and 22will preferably not be directly connected.

Until the ready signal develops on the pin 12, the output of anamplifier 30 is maintained at the same voltage as the camera referencesignal at the pin 24 by means of biasing resistors 29 and 31 and aprotective diode 27. The resistors 29 and 31 and the diode 27 providegood standoff protection in the event a high voltage signal isinadvertently connected to the terminal 22. Power for amplifier 30 andthe remaining circuitry of FIG. 2 is provided by a power supplyindicated generally at 25 and connected to the capacitor anode voltageof the flash via the terminal 14.

When the flash ready signal develops on the pin 12, the output of theamplifier 30 goes low and causes current to be drawn from the referencevoltage supplied at the terminal 24 through one of resistors 23a or 23b,depending on the state of switches 21a and 21b. The switch 21a isprovided to permit use of the "dark sync" feature available on certaincameras such as the Canon A-1, wherein shutter speeds slower than normalflash synchronization speed may be manually selected. The switch 21bpermits the adapter to be used in a manual mode by disconnecting theaperture setting signal discussed hereinafter from the terminal 26.

Once the amplifier 30 causes current to be drawn from the referencevoltage at terminal 24, a camera such as the Canon AE-1 provides a flashready signal to the shutter. This causes the shutter to interlock at theflash synchronization speed regardless of the position of the shutterspeed selector dial on the camera. At the same time, the referencevoltage at the terminal 24 is also supplied to a buffer amplifier 32where it is multiplied. Typically, the reference signal may be nominally1.3 volts, and will be doubled by the buffer amplifier 32 although anyother multiple, including fractional multiples, is suitable. Themultiplied output signal of the amplifier 32 is supplied to a line 34,which connects to one terminal of the body 36 of a variable resistance37. The remaining terminal of the body 36 of the variable resistanceconnects to the common signal, or ground, at pin 16 of the connector 10and likewise at pin 28 of the connector 20.

As will be discussed hereafter in connection with FIG. 2, the body 36 ofthe variable resistance is movable with respect to the wiper 38 thereofto provide an indication of film speed, or ASA. The wiper arm 38 of thevariable resistance is mechanically connected to a graded densityoptical filter 40 placed in front of a photosensor 42 (better shown inFIG. 3). As further shown in FIG. 3, the wiper arm 38 and optical filter40 are jointy movable to provide a continuous indication of rangesettings. The wiper 38 and body 36 of the variable resistance are eachtherefore relatively movable to provide continuous settingsrepresentative of film speed and range.

Once the position of the body 36 of the variable resistance 37 and wiper38 have been set for the particular photograph, the multiplied referencesignal on the line 34 is then voltage divided by the variable resistance37. The result is a reduced signal at the wiper arm 38, which issupplied as one input to a scaling amplifier 44. The remaining input tothe scaling amplifier 44 and associated circuitry is provided by thereference signal from the camera on pin 24.

Depending upon the gain of the amplifier stage 32, the gain of theamplifier stage 44 may be less than unity. The purpose of the amplifierstage 44 is to scale the aperture setting signal provided on wiper arm38 to be compatible with the circuitry of the particular camera. Forexample, for the Canon AE-1, a voltage change of nominally seventy-fivemillivolts with respect to the reference voltage on the pin 24 indicatesan aperture change of approximately one stop. Also, the referencevoltage typically represents an aperture setting of f/4, so that theincrement representative of an aperture change may be either positive ornegative with respect to the reference voltage. Also, the scalingamplifier 44 buffers the relatively high impedance variable resistance37, which may for example be on the order of twenty kilohms, to preventundue loading on the relatively low impedance exposure control circuitryof the camera.

Thus, by providing a signal on the line 34 which is greater than thereference voltage at pin 24, it is possible to provide a bipolar rangeabout the reference signal. Then, where the signal available at the line34 permits greater than a seventy-five millivolts increment to indicateone f/stop change in aperture, the scaling amplifier 44 may have a gainof less than unity. This is advantageous because it provides aproportionate reduction in any sensing or integrating errors which maydevelop in the preceding portions of the circuit. When the properlyscaled aperture setting signal from the amplifier stage 44 is providedto the camera via the pin 26, the circuitry of the camera causes thediaphragm to adjust to the proper setting for the particular range andfilm speed information supplied at the variable resistance 36.

Once the flash is triggered, the light is reflected from the scene andpasses through the optical filter 40 onto the photosensor 42 and itsassociated capacitor 46. This provides a signal to the turn-offcircuitry of the flash via the pin 18 to cause the flash to limit theemitted light to an amount appropriate to the selected aperture. Thus anew and novel method of encoding information has been disclosed. In theevent it is desirable to operate the flash in a manual mode so that theswitch 21b is in the manual position, and also to reduce the amount oflight emitted by the flash as in the case of flash fill, weightedresistors may be connected between a line 47 and the terminal 28(ground) together with a suitable switching means (not shown) forselecting either the automatic mode or the desired manual setting. Suchvariable power settings are available in the Vivitar Model 285 flash.

Referring now to FIG. 3, there is shown therein a mechanical arrangementfor one embodiment of the sensor portion 7 only of the adapter of thepresent invention. The sensor portion is a portion of the adapter 1shown in FIG. 1 and FIGS. 4a-4c. A housing 100 forms the connector 10and encloses the pins 12, 14, 16 and 18 as well as the remainder of theapparatus. Enclosed within the housing is a fixed shaft 102, whichsupports a rotatable metal shaft 104. Affixed to the end of the shaft102 is a cover 106, which houses a lens or other suitable lightgathering means 108 in a passageway 110 therethrough. Affixed to theshaft 104 and rotatable therewith is a ring or plate 112, a portion ofwhich includes the optical filter 40 shown in FIG. 2. The wiper 38associated with the optical filter 40 connects between the rotatableshaft 104 and the body of the variable resistance 36, which is affixedto another rotatable member 114. The terminals of the body of thevariable resistance 36 have been supplied to the associated circuitryshown in FIG. 2 and located on a printed circuit (PC) board 116 via apair of wipers 118 and 120. The position of the wiper 38 is communicatedto the PC board via the conductive shaft 104 and another wiper 122. Itcan thus be seen that both film speed (ASA) and range may be readilyaltered merely by rotating the appropriate members 112 or 114. In theevent a variable power feature is desired, an additional rotatablemember may be included for selecting the desired weighting resistor.

Rotation of the member 112 causes the setting of the potentiometer forvariable resistance 36 to vary, and also varies the optical density ofthe filter 40 in front of the sensor 42, also located on the PC board116. The optical filter 40 may be a wedge filter or other suitablefiltering means, and provides direct coupling between the optical systemand the exposure control circuit to the automatic exposure camera. Itcan therefore be appreciated that the system of the present inventionprovides a new and novel means of formatting information for use in anelectro-optial system. It can further be appreciated that the system ofthe present invention permits a non-dedicated automatic flash to be usedin conjunction with the automatic exposure control system of a camera.

Referring again to FIG. 1 and also to FIGS. 4a-4d, the mechanicalfeatures of the adapter 1 of the present invention may be betterappreciated. As can be seen from FIGS. 1 and 4a, the adapter 1 couplesto the flash at both the socket 8 and the foot 4 of the flash 2 by meansof the connector 10 and the shoe 5, respectively. For ashutter-preferred camera such as the Canon AE-1, the sensor portion 7 ofthe adapter 1 is formed integrally with the housing 9. However, forother automatic exposure cameras such as the aperture-preferredautomatic exposure cameras manufactured by Olympus, Nikon and Minolta,the housing 9 will include only a connector 10 and another socket 7 intowhich the normally supplied sensor, such as the removable sensorsupplied with the Vivitar Model 285 flash, may be connected. The shoe 5of the adapter includes a conventional flash trigger terminal 140 andground terminal 142.

As noted previously, one of the many advantages of the present inventionis that it permits an automatic flash to be operated remotely inconjunction with the exposure control circuitry of an automatic exposurecamera, while still monitoring the reflected light received at thecamera. This is accomplished by detaching the flash from the adapter 1and connecting the socket 7 to the connector 10 by means of aconventionally available cable (not shown) such as that manufactured byVivitar Corporation. This leaves the photosensor portion of the systemlocated at the camera to monitor reflected light, while permittingremote location of the flash itself. Because the adapter 1 includes thecircuitry for making the flash compatible with the particular camera,access to the camera's exposure control circuitry is maintained.

Referring now to FIGS. 4b-4d, additional features of the presentinvention can be better appreciated. FIG. 4c shows in plan view the shoe5 of the adapter 1, into which the flash 2 slides. FIGS. 4b, 4dillustrate in cross-sectional side view the assembly of the flash foot4, the shoe 5, the base 6 and the camera accessory shoe 3. The shoe 5includes a deformable insert 150 which extends through the shoe 5 to thespace above the base 6 into which the accessory shoe 3 fits. Thedeformable insert 150 operates in conjunction with a locking mechanismsuch as that found on the Vivitar Model 285 flash to securely fasten theflash to the adapter and also fasten the adapter 1 to the accessory shoe3.

The deformable insert 150, which may for example be made of Delrin orother suitable material, includes a pair of flat plates 152 and 154located between the upper portion of the foot 4 and the base plate 156(FIG. 1) thereof on the flash 2. When the locking mechanism of the flashis actuated, a resilient plate 158 on each side of the foot 4 is drivendownward onto the deformable insert 150 at the plates 152 and 154. Theforce on the plates 152 and 154 causes them to deform slightly, in turndeforming a pair of ears 160 and 162 associated with the plates 152 and154, respectively.

The ears 160 and 162 extend through the shoe 5 to the space above thebase 6 and also above the camera accessory shoe 3 (FIG. 4b). When theflash locking mechanism is actuated to cause the ears 106 and 162 todeform, the ears 160 and 162 are forced down onto the top of theaccessory shoe 3, thereby locking both the flash 2 and the adapter 1onto the camera (FIG. 4d). When the flash locking mechanism is released,the insert 150 returns to its original position and the flash, adapterand accessory shoe may be easily separated.

Having fully described one embodiment of the present invention, it is tobe understood that many equivalents and alternatives which do not departfrom the spirit of the invention will be apparent from the teachingshereof to those skilled in the art. It is therefore to be understoodthat each of these alternatives and equivalents which do not depart fromthe spirit of the invention are intended to be included herein.

What is claimed is:
 1. An adapter for connecting a camera and a flashunit wherein the flash unit includes a source of electrical power, aflash tube, flash initiating means for triggering the flash tube tocause it to emit light, and flash-termination means for terminating theflash of light from the flash tube, said adapter comprsing,cameraterminals for connection to a camera, flash unit terminals forconnection to said flash unit, synchronizing means for coupling thecamera and flash unit terminals for conveying a synchronizing signalfrom the camera to the flash unit for initiating operation of the flashinitiating means, photographic parameter means for conveying a signalfrom the flash unit to circuit means of the adapter for causing aphotographic parameter signal to be applied to the camera, said circuitmeans including means for conveying to the flash unit a flashtermination signal for causing the flash-termination means of the flashunit to terminate the flash of light from the flash tube, and means forsupplying said circuit means with operating power from the source ofelectrical power of the flash unit through said flash unit terminals. 2.An adapter as in claim 1 wherein said circuit means of said adapterprovides a signal for causing an aperture setting signal to be appliedto the camera when the flash unit is in a predetermined operativecondition.
 3. An adapter as in claim 1 whereinsaid circuit means of saidadapter causes the shutter speed of the camera to be set to anappropriate speed for flash photography when the flash unit is in apredetermined operative condition.
 4. An adapter as in claim 1whereinsaid circuit means of said adapter includes a light sensor forreceiving light and providing said flash termination signal.
 5. Anadapter for interconnecting a camera and an electronic flash unitwherein the flash unit includes capacitor means for providing a sourceof electrical power and said capacitor means including a capacitor, aflash tube, discharge means for discharging said capacitor through saidflash tube, and flash-termination means for terminating the discharge ofsaid capacitor through said flash tube, said adapter comprisinga set ofcamera terminals for connection to said camera, a set of flash unitterminals for connection to said flash unit, reference means in saidadapter coupled to at least one of said sets of terminals for providinga common electrical reference, signal means within said adapterconnected to said reference means and to one of said flash unitterminals and to one of said camera terminals for responding to an inputsignal from one terminal and applying a signal to the other, means forsupplying said signal means with operating power from said source ofelectrical power through said set of flash unit terminals, andsynchronizing means coupling additional ones of said camera and flashunit terminals for conveying a synchronizing signal from said camera tosaid flash unit for initiating flash development by said flash unit. 6.An adapter for connecting an electronic flash unit with a camera andwherein the flash unit includes a source of electrical power, saidadapter comprisinga set of camera terminals for connection to a camera,a set of flash unit terminals for connection to an electronic flashunit, reference means in said adapter coupled to at least one terminalof one of said sets of terminals for providing a common electricalreference, signal means within said adapter connected to said referencemeans and to one of said flash unit terminals and to one of said cameraterminals for responding to an input signal from one terminal andapplying a signal to the other, means for supplying said signal meanswith operating power from said source of electrical power through saidset of flash unit terminals, and synchronizing means coupling additionalones of said camera and flash unit terminals for conveying asynchronizing signal from said camera to said flash unit for initiatingflash development by said flash unit.